$post_date is set to GMT (get_date_from_gmt()) value of $dateCreated (assuming it's GMT)
and then $post_date_gmt is set to GMT ...

this forces both values to be identical and assumed to be GMT. this also breaks the ability to set the timezone in the value of dateCreated even though the ISO8061 spec allows it.

I've attached a patch to class-wp-xmlrpc-server.php which appears to fix this problem and allows future published posts to publish properly at the expected date/time.

to duplicate, use an XML-RPC client (I'm using a Perl script) to add a new post and set the dateCreated to a dateTime.iso8061 entity with the value of '20111019T19:05:00+0900' (or something equivlent for your timezone which would be easy to identify as an incorrect value if so.) the publish date of the new post will be the GMT value.

A workaround would be to do all the GMT conversion in the client prior to sending via XML-RPC, but that would make it seem that dateCreated and date_created_gmt will always be duplicate. I've included a patch in case this wasn't an intentional design decision.